PROJECT SUMMARY/ABSTRACT This proposal describes Phase II of the development of a rapid immunoassay test kit for the determination of hemoglobin variants in blood, to be used as a point-of-care diagnostic test for sickle cell disease (SCD) and SCD carrier trait in low-resource settings worldwide. Today, determination of SCD and SCD trait requires lengthy and expensive laboratory analyses that are not available in low-resource settings, and >80% of individuals with SCD and SCD trait live in areas where healthcare is provided in those settings. Nevertheless, newborn screening programs have resulted in significant improvement of patient outcomes due to early treatment to prevent complications of the disease. The proposed test kit will be a lateral flow immunoassay, similar in principle to a home pregnancy test. The test design is based on monoclonal antibodies (MAbs) specific for the single-amino-acid differences between SCD-related hemoglobin variants. In Phase I, the applicant developed a working prototype hemotyping test kit which was shown to correctly identify the phenotype of >99% of tested whole blood samples, including each relevant SCD and carrier phenotype. The prototype test requires a 1-microliter volume of blood and the time-to-result is under 20 minutes. In Phase II, the test kit will be further improved and simplified, and a complete manufacturable product will be developed. Clinical validation studies will be carried out to determine the real-world performance of the product, including studies performed in low-resource settings in Brazil. At the successful conclusion of Phase II, the test kit will be ready for manufacturing and submission for approval to regulatory agencies worldwide. The estimated cost of the hemotyping test kit will be $2.00, a price point that will allow widespread acceptance of this test kit in developing countries.